This trainer is same as Fiber Optic Pulse code modulation trainer Model FOT-7. The only difference in PCM-1 is that a connecting patch cord is used instead of Fiber Optic cable. Otherwise it is the same as FOT-7. The purpose of this trainer Model PCM-1 is to introduce you to the Pulse Code Modulation (PCM) and demodulation technique. A multimode Fiber Optic cable is used for data transmission and reception. In this trainer, you will understand and investigate the following processes. All the major blocks of this trainer are designed from fundamental building blocks instead of using a dedicated CODEC. As a result, all the blocks of CODEC are dissected and are available as separate building blocks for study. This facilitates the student to understand the quantization process and view the quantified and encoded data using 8 bit LED displays at the transmission side. Observe the serial transmission and reception of this quantified decoded data at a test point, observe the decoded 8 bit received data on LED display etc. This data is further reconstructed and the original signal is available at an output terminal for analysis. As a result of this design, the student can see various stages of the PCM transmission and reception processes for himself. Features of PCM blocks are - Digitization of an analog signal,
- Observe the quantization (encoding) of incoming signal,
- Measurement of quantization noise,
- Serialization of quantized signal for onward transmission,
- Serial data capture,
- Decoding of quantified signal,
- Observation of received signal,
- Reconstruction of received signal, and
- Study of aliasing.
In order to achieve the above, the trainer has necessary built in input signal sources.
a) Continuously variable analog input in the range of 0 to 5 VDC,
b) Function generator with Sine, and Square wave inputs in the range of 200Hz to 20KHz
c) Microphone input after proper signal conditioning, for voice transmission and
d) Provision to connect an external signal source. The output of the transmitted and received signals, decoded signal and finally the reconstructed outputs can be observed on the oscilloscope. In order to observe the sequence of events taking place, there are two types of clocks provided, one operating at 200KHz, the other at 1Hz. During slow clocking it is possible to observe the signal flow at various test points as detailed below. a) Quantization process
b) Serial transmission
c) Decoded output and
d) Reconstructed output.
e) A power amplifier with speaker to hear the voice reception ( when sampled at 200KHz) This trainer comes with completely self-contained systems with built-in power supplies, signal sources, input output test points for signal observations, a microphone with proper signal condition, a power amplifier with speaker etc. This requires an optional external Dual beam oscilloscope to observe the PCM signal transmission at different stages of modulation and demodulation processes. Specifications:
Input sources: 1. Built-in Function generator with SINE, and SQUARE waveforms.
2. Frequency: Variable frequency of 200Hz to 2KHz
3. Amplitude: Variable in the range of 0 to 5 Volts
4. Continuously variable DC source : 0 to 5V DC
5. Provision for connecting external signal source Output: 1. 8 bit LEDs to display Quantized data
2. 8 bit LEDs to display decoded data
3. Power amplifier with speaker
4. Frame timing LED to display clock signal
5. Synchronizing signal LED
Built-in power supplies. All the above are available in an ergonomically designed cabinet. |
